The present invention relates generally to electrical connectors, and particularly to an electrical connector providing good electrical and mechanical connecting and holding capabilities while also being inexpensive to manufacture.
Conventional set screw connectors generally provide a smooth, round bore surface for accepting and seating a conductor or cable inserted into the bore. Such structures tend not to provide extraordinary conductor holding ability, the set screw being the only item providing a biting action into the conductor to retain the same within the body of the connector.
In addition, in many prior set screw devices, when a set screw is moved against the conductor and the conductor against the contact surface of the connector in the process of effecting the connection, the material of the conductor tends to be extruded in opposed directions along the contact surface so that shear in the conductor in the direction of set screw travel is minimal. Hence, to assist in dislodging any dielectric oxidation on the conductor and the contacting surface of the connector body, and to improve somewhat the holding ability of the connector, protrusions or intrusions (indents or serrated surfaces) are sometimes provided on or in the contacting surfaces. Such protrusions or intrusions, however, add costs to the connector since they are generally provided by machining operations which are performed in addition to the basic process of making the connector body.
There is a group of connectors in which the above problems can be at least partially alleviated, these connectors involving the use of a base and keeper having leg or body portions interdigitally disposed, with aligned openings in such portions adapted to receive a conductor or cable to be connected by the device. In connecting a conductor, the base and keeper are moved in opposed directions against the conductor, the base and keeper providing multiple seats for engaging the conductor and for placing the conductor in shear. Such devices are shown in Swiss Pat. No. 419,275 and in Fotsch, Thomas, Locher and Hawkins U.S. Pat. Nos. 2,086,710; 2,112,053; 3,129,996 and 3,829,825, respectively. In the patent to Hawkins, the legs of a base and keeper are placed in tension against the conductor, the tension, and thus the connecting force being maintained by the resilient characteristics of the base and keeper, as explained in the patent, the base and keeper having both a transverse and longitudinal spring characteristic. (The embodiment of FIGS. 14 and 15 in the Hawkins patent is an exception to the tension principle disclosed in the patent.)
In these patents, two basic components (a separate base and keeper) are required. It can be appreciated that each item and each manufacturing step in making the item and assembling the connector involves costs that are reflected in the ultimate selling price of the connector and that any reduction in the number of components and manufacturing steps will produce a corresponding reduction in the costs of the connector. However, in making such reductions, it is necessary that the quality of connection not be also reduced, i.e., it is preferable that the holding ability of the connector be improved and it is necessary that any oxidation on the connector and on the conductor be dislodged in the connecting process to a degree and in amounts sufficient to provide a minimum or zero electrical resistance between the conductor and the connector body.
A single piece electrical connector is shown in British Pat. No. 1,295,391, the connector comprising a body made of bent sheet metal, the upper wall of the connector having overlapping wall portions. In FIG. 2 of the patent, the side and bottom walls of the body are deeply slotted to provide the same with a flexibility that is greater than the upper, overlapping wall of the connector, the bottom wall of the connector comprising only a narrow neck 9 of flexible material.
In U.S. Pat. No. 3,609,657, issued in the name of Harris I. Stanback, an electrical connector is shown employing two set screws located in a single connector body on opposed sides of the longitudinal axis of a cable received in the body, the two screws displacing the strands of the cable against the sides and bottom of the cable receiving bore of the connector body. In the connector of this patent, the connecting body and base surface have no windows or openings so that any shear of the cable is in directions normal to the travel of the set screws, in the manner explained above.